Results 1 to 3 of 3
Like Tree1Thanks
  • 1 Post By emakarov

Math Help - Problem with matrices question, finding A^2

  1. #1
    Newbie
    Joined
    Jul 2012
    From
    USA
    Posts
    1

    Problem with matrices question, finding A^2

    The question is this one below:

    Let
    A =
    (1 -3)
    2 0

    How am I supposed to find A^2?


    Also Let
    B =
    (-6 3 )
    8 20

    How do I find Matrix X such that 5X-A=B ?



    Full explanations would be nice, someone tried to explain it to me briefly but I didn't quite understand it.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor Reckoner's Avatar
    Joined
    May 2008
    From
    Baltimore, MD (USA)
    Posts
    1,024
    Thanks
    75
    Awards
    1

    Re: Problem with matrices question, finding A^2

    Quote Originally Posted by DaveWolfgang View Post
    How am I supposed to find A^2?
    A^2 = A\cdot A = \left[\begin{array}{cc}1&-3\\2&0\end{array}\right]\cdot\left[\begin{array}{cc}1&-3\\2&0\end{array}\right]


    Quote Originally Posted by DaveWolfgang View Post
    How do I find Matrix X such that 5X-A=B ?
    You know that X has to be a 22 matrix for the subtraction to be valid. If we let

    X = \left[\begin{array}{cc}a&b\\c&d\end{array}\right],

    then

    5X - A = B

    \Rightarrow5\left[\begin{array}{cc}a&b\\c&d\end{array}\right] - \left[\begin{array}{cc}1&-3\\2&0\end{array}\right] = \left[\begin{array}{cc}-6&3\\8&20\end{array}\right]

    \Rightarrow\left[\begin{array}{cc}5a-1&5b+3\\5c-2&5d\end{array}\right] = \left[\begin{array}{cc}-6&3\\8&20\end{array}\right]

    Now equate the corresponding entries.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor
    Joined
    Oct 2009
    Posts
    5,536
    Thanks
    778

    Re: Problem with matrices question, finding A^2

    Quote Originally Posted by DaveWolfgang View Post
    How do I find Matrix X such that 5X-A=B ?
    Or just X = (1/5)(B + A).
    Thanks from Reckoner
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Matrix problem: Finding all matrices A such that AM = - MA
    Posted in the Advanced Algebra Forum
    Replies: 2
    Last Post: May 14th 2011, 06:12 PM
  2. Finding Elementary Matrices
    Posted in the Advanced Algebra Forum
    Replies: 1
    Last Post: March 7th 2011, 02:01 AM
  3. Tables word problem - finding matrices
    Posted in the Advanced Algebra Forum
    Replies: 1
    Last Post: February 3rd 2010, 06:26 AM
  4. Finding two matrices that multiply to...
    Posted in the Advanced Algebra Forum
    Replies: 4
    Last Post: January 28th 2010, 12:17 AM
  5. Finding all 2 by 2 matrices that have eigenvalues x and y
    Posted in the Advanced Algebra Forum
    Replies: 1
    Last Post: April 5th 2009, 04:46 PM

Search Tags


/mathhelpforum @mathhelpforum